unstable internet connection specialty old device

[raminehgdr71]

From the first day, when I connected to the internet especially my phone and old laptop, the internet is turn on and off and I have to disconnect my phone(off/on wifi phone) and again connect it in order to access the internet. my new laptop does not have this problem but the phone and the old laptop have this problem. my phone and the old laptop is completely healthy and do not have any problem with other modems. 

My modem model : tg3442de vodafone 

Edit: Thread moved to matching board. DSL-->Kabel. BR WolfgangF

[Wallace]

Hi,

a connection with the router is established, but the devices do not get an IP?

Regards

Wallace